Method for repairing the surface of a board-shaped carrier

ABSTRACT

The invention relates to a method for repairing the surface of a board-shaped formwork element. According to the invention , it is provided that a formwork board has a coating that is meltable under the influence of heat, which, after having been damaged, is at first removed in part, the removed part being replaced by a new cover foil that is connected to the remaining coating by welding. Therefore, when repairing the formwork boards, individual defects of the coating or the formwork facing need not be elaborately touched up. Rather, industrially produced foils with a good surface quality can be applied over a large area. The formwork boards or elements thus designed satisfy the operational requirements of price, simple repair that can, if necessary, be fully or partly automated, robustness and surface quality particularly well. The surface of a formwork element can cheaply and simply be designed so as to be reusable, with no blemishes, repairs or weaknesses showing on the surface of the formwork facing facing the concrete of a formed building.

The invention relates to a method for repairing the surface of a board-shaped carrier having a coating on at least one side that can be melted under the influence of heat. In particular, the invention relates to a method for repairing formwork elements, as well as to the board-shaped carrier or the formwork element itself.

Formwork elements serve the purpose of erecting concrete buildings and keep the unhardened concrete in shape until it has hardened. Formwork elements, as a rule, consist of a frame and a board-shaped formwork panel, hereinafter referred to as board-shaped carrier. Numerous methods for repairing such formwork elements or formwork panels are known from the state of the art:

It is known (DE PS 28 48 1 54) to produce formwork elements or formwork panels from wood, for example plywood. Such formwork elements are disadvantageous in that they swell up when penetrated by moisture. Under great strain, the protective impregnating layer is destroyed and the surface frays out. Thus, it offers an additional point of attack for enterin water. Nail holes made in the formwork element in use also lead to damage to the veneer layer or the protective impregnating layer, so that water can also penetrate there. Finally, transport and handling of the known formwork elements during the rough work on construction sites lead to damage of the surfaces to be produced with concrete, in the visible area of the formwork facing. The life span of such formwork elements consisting of plywood is thus limited.

Known formwork elements such as formwork panels can be repaired, for example by filling small blemishes or even by using repair disks in the case of damage over a greater area. However, the surface of the plywood board is thus structured, which is not desirable when erecting or producing concrete surfaces.

Though known formwork elements consisting of plastics (EP 0 250 730 B1 and DE 38 04 506 A1) do not exhibit swelling due to entering water, as plywood boards do, but, just as plywood boards, they have to be repaired elaborately and manually in the visible area if they have been damaged during use and in particular on the surface. After cleaning the formwork elements or formwork panels by means of a high-pressure water jet or by means of rotating brushes, scratches, nail holes and drill holes on the surface must be touched up. It is known to touch up thermoplastics by weld-facing with a hand-held welding device, Then, the defect thus filled must be milled plane with a router to be guided by hand, drill holes and damages with a surface area must be milled out cleanly and closed with plastic discs. In the case of formwork elements of thermosetting plastics, the same repair measures are necessary as in the case of a plywood board.

Even if utmost care is taken when repair measures are carried out, they still become visibly apparent on the surface of the concrete buildings erected by means of these formwork elements. Formwork elements are often rented from the producers and suppliers of such formwork elements for upcoming building projects. Thus, a large part of the used formwork elements is not purchased anymore, and repaired in one's own company if necessary, but rented on demand and in a fully functional state. The lesse expects an intact surface of the formwork facing without surface structures, also in the case of formwork elements that were used before by third parties. Therefore, the lessor must therefore touch up damages of the formwork elements prior to renting them out again, which not only is complicated but also incurs considerable costs.

Formwork elements whose board-shaped carriers are covered on one side with a foil that forms the formwork facing and is exchangeably attached on the carrier by means of an adhesive that can be deactivated under the influence of heat (EP 1 273 738 A), cannot be used optimally if environmental conditions are very warm, because in hot countries, the adhesive is undesirably deactivated under strong insolation, i.e., it can become viscous.

Therefore, the invention is based on the object of providing an improved method for repairing formwork boards or formwork elements.

This object is solved according to the invention with a method for repairing the surface of a board-shaped carrier according to claim 1. Moreover, the object is solved by a board-shaped carrier according to the independent claim. Advantageous embodiments are the subject matter of the dependent claims.

At first, it is provided according to the invention that a formwork board has a coating that is meltable under the influence of heat, which, after damage has occurred, is at first removed in part, the removed part being replaced by a new cover foil that is connected to the remaining coating by welding. Therefore, when repairing the formwork boards, individual defects of the coating or the formwork facing need not be elaborately touched up. Rather, industrially produced foils with a good surface quality can be applied over a large area. Compared to other joining techniques, such as, for example, gluing, the following advantages are the result: repairing the formwork surface again is more difficult in the case of adhesives, since this is a material composite. It is difficult to remove the residue of the adhesives, which also impairs the joining quality, A base provided with glue is more difficult to prepare, so that the remaining coating would have to be removed slightly more deeply with each new repair. Ripping, smearing and uncontrolled removal movements would occur when the top side of the coating is removed, e.g. by milling. In addition, the waste consists of several components, which makes recycling or disposal more difficult. Applying glue over a surface area is more difficult and in the majority of cases involves the release of solvents. In addition, glues require hardening times that delay the production process. Welding on a new cover foil can be done almost any number of times, in particular when the cover foils and the remaining coating consist of the same material. This extends the life span of the formwork board.

The formwork boards or elements thus designed satisfy the operational requirements of price, simple repair that can, if necessary, be fully or partly automated, robustness and surface quality particularly well. The surface of a formwork element can cheaply and simply be designed so as to be reusable, with no blemishes, repairs or weaknesses showing on the surface of the formwork facing facing the concrete of a formed building.

According to the invention, the damaged formwork facing or foil of the formwork panel of a multi-layered formwork element or panel provided as a surface can be substituted or refaced in a simple manner. For example, formwork elements of a modular frame formwork can be prepared for reuse in this manner. For refacing the formwork facing, it is specifically removed in part without making the carrier system itself unusable and damage it. After removing the surface of the worn and damaged formwork foil, a new cover foil or formwork foil is applied to the reusable formwork panel and attached to it. Damages of the formwork panel or the carrier system do not become apparent on the surface of the formwork element owing to the applied new full-area surface. According to the invention, a multi-layered formwork element can be made suitable for reuse with an appropriate production effort, avoiding time-consuming repair and touch-up work of the formwork facing, without irritating surface structures becoming apparent on the surface of the formwork element. Thus, scratched or otherwise damaged surfaces of formwork elements are replaced by new formwork facings or formwork foils. In other words, the formed formwork element or the carrier is coated with a new formwork foil on the side facing the concrete, according to the invention. Therefore, the formwork element according to the invention consists of at least two main functional elements, namely a carrier system or the formwork panel and a coating, i.e. formwork foil or formwork facing, whose surface can be removed and welded on again. The formwork foil forms the actual contact surface with the concrete, and is responsible for the structuring of the surface as well as the surface quality of the concrete. The carrier system or the formwork panel itself is formed such that it provides the required load-bearing capacity. In this case, multi-layered systems may also be used in order to reinforce the formwork panel or the carrier system.

Milling is a method that can be controlled well for the large area removal of thin layers, and it is more suitable than smoothing due to the large removal. Blade milling machines are preferred because they are better adapted to the soft ductile material of the coating. If a plurality of blades are used in the blade milling machine, undesired rattling can be avoided. Because the blades may be distributed over the blade milling machine so that they are not all used at the same time or under the same angle. The blades distributed in axial direction therefore bite into the surface of the coating at slightly different times. Usually, a small overlap of the area that adjacent blades bite into is provided so that the formation of ridges running in the feeding direction is excluded. Depending on the parameters of feeding speed (i.e. relative movement between the milling machine and carrier), diameter of the milling machine, number of blades and rotational speed of the milling machine, the result is a perfectly plane or slightly wavy surface of the remaining coating. A slight waviness can even be desired in order to make it easier to melt on the remaining coating during welding. In addition, inhomogeneities can be compensated during melting-on, when the cover foil is pressed on the remaining coating.

In order to avoid sudden strains, when the milling tool bites into the surface of the carrier, and processing inaccuracies connected therewith, the milling machine is disposed obliquely in relation to the feed. That means that the milling machine does not bite into the entire edge length of a board coming into the area of the milling machine at the same time, but starts, for example, at the front left edge of the board and seizes the entire width of the board only during the continued feed. This reduces mechanical strains and improves the surface quality.

The method preferably is carried out continuously, so that melting-on does not become necessary over a large area, which entails large investments. In the continuous method, welding is carried out over the length of the carrier, with the melting-on and welding being done immediately one after the other in a strictly limited area.

When the cover foil is melted on, it is entirely sufficient to only bring the underside into the liquid state so that less energy is consumed and less time is required. The thickness of the cover foil as well as its surface is substantially maintained.

No additional material is to be inserted between the remaining coating and the cover foils during welding. Thus, their chemical composition does not change even in the case of multiple repairs of the coating. The worn surface can be removed with reproducible quality and the same parameters and a new cover foil can be welded on time and again. The removed material is type-specific and can thus be better recycled.

Heat lamps, in particular infrared heat lamps, short-wave twin tube lamps and the like are used during welding. This is an uncomplicated, inexpensive technology whose heating power can be adjusted and adapted in a reproducible and continuous manner over a wide range, if necessary automatically dependent on the process.

When the cover foil is guided around a roller in the area of the welding zone, the underside of the cover foil and the top side of the remaining coating are visible at the same time from one direction in the welding zone. Thus, both foils can be heated at the same time with one heat lamp. It can be expedient for optimizing the melting-on process that the heat lamp is pivotable, so that the introduction of heat can be shifted for the benefit of the cover foil or the remaining coating.

In the process, the roller for diverting the cover foil can press the cover foil against the remaining coating at the same time, and thus initiate or support the actual welding process. Advantageously, the heat distribution is designed such that the material is already sufficiently cooled or hardened when it leaves the roller. Alternatively, this may also be done by additional subsequent pinch rollers.

It is necessary to straighten the repaired carrier, because a bending of the carrier occurs after the welding as a consequence of the cooling stresses. The bending can be corrected by the usual straightening after the welding. However, pre-bending after the milling and before welding is advantageous: straightening would be required anyway prior to welding and after the milling, where a bending of the board also occurs due to the removal of a part of the coating. For this reason, it is proposed according to the invention to carry out the straightening, which would anyway be necessary after the removal by milling, right away so that a pre-bending of the carrier is generated that can be neutralized again by the internal stresses introduced by welding. Thus, only one straightening process is necessary instead of two. Another measure against bending due to internal stresses is the introduction of heat from both sides during welding in order to generate stresses symmetrically.

Depending on the development of the formwork elements, in which the above formwork boards or board-shaped carriers are inserted in a frame that gives stability, it may be necessary to take the carriers out of the frame. Even if it is not technically imperative to take them out, it nevertheless has advantages with regard to the transport of the carriers to the repair system. The carriers, which substantially consist of only one board, can be stacked in a manner that saves substantially more room. In a continuous coating method, the carriers that are disposed behind one another can be repaired very effectively. If the size and the geometry of the formwork element permits, it is preferred to repair the formwork element according to the invention without the time-consuming removal of the carrier.

If the method according to the invention is repeated several times, the life-span of the carrier is extended. The method can also be carried out on both sides of the carrier, if the carrier board is developed appropriately, for example, symmetrically. This doubles the practical life-span of the board. In case of possible irreparable damages to one side, at least the second side can be used further.

The carrier described according to the invention, with the exception of the coating repaired by welding on a new cover layer, is basically known in formwork construction, for example under the brand name LAMINAEX Al PP by the company Isosport, A-7000 Eisenstadt. These are boards with a core of extruded PP foam. Reinforcement boards of aluminum are provided on both sides for reinforcement, i.e. for increasing the bending resistance. A foil of PP as a formwork-facing forming coating is applied to them by means of a special continuous process. It is easily detachable from the hardened concrete. The connection between the aluminum board and the PP material, which is demanding to produce, can thus be carried out safely and industrially. The connection between the materials remains over the entire life-span, because it is not removed when the carrier is reprocessed. Thus, only tools of a simple construction are necessary for recoating.

The formwork elements or carriers according to the invention may, for example, have a three-layered of five-layered structure, depending on the extent of mechanical stress, however, a two-, four or multi-layered structure is also possible. Plastics with or without reinforcements or wood materials such as plywood or chipboards are used as the material for the carrier system or the formwork panel. Metallic material, in particular steel, aluminum and other materials are also conceivable. A sufficient rigidity must be provided for the formwork elements, in particular in wall formwork and wall supports. If necessary, the carrier system may be reinforced by a metal foil or also by fibers. The formwork foil can be a foil or board of plastics, preferably of polyproylene (PP), polyethelene (PE) and/or polyvinyl chloride (PVC). Constructionally, the formwork element according to the invention is formed as a composite structure. The individual functional layers are connected with each other in a sandwich construction. The individual functional layers are connected with each other by means of adhesives.

The dimensions specified in the claims resulted as a favorable compromise as regards costs and benefit. In particular the ratio of the remaining coating to the thickness of the coating is selected such that the new cover foil is not unnecessarily thick, and that on the other hand a good surface quality is ensured even in the case of greater damage.

The re-coating of the entire modular frame formwork element leads to a substantial reduction of cleaning and repair costs, because, additionally, the dismantling and assembly of the formwork facing can be dispensed with. The cleaned modular frame formwork elements are customized as regards their width and height and are subsequently fed into the recoating system again. It is also possible to incorporate the cleaning process into the recoating system. The surface is removed from the carrier system in the subsequent removal process. If the carrier system remains connected with the frame during the entire removal and recoating process, fastening elements such as rivets or bolts between carrier system and frame are designed so as not to have a negative effect upon the recoating process.

By means of the method, particularly large boards can be reprocessed automatically, cost-effectively and with a defined surface. Large boards preferably have a length of more than 2 m, preferably 2.40 m. Depending on the element, the width is at least 30 cm, preferably 75-90 cm.

The top side of the coating or of the cover foil is smooth, i.e., it has such a surface that the result is the usually desired smooth exposed concrete surface.

Further advantages become apparent from the following description and the attached drawing. Also, the above-mentioned features, which are developed further, according to the invention can each be used individually or in arbitrary combinations. The embodiments mentioned shall not be understood to be final, they have the character of examples. The drawings show:

FIG. 1. a formwork board known from the prior art,

FIG. 2. the formwork board of FIG. 1 after the top side has been milled off;

FIG. 3. welding a new cover foil onto the remaining coating; and

FIG. 4. the repaired carrier from FIG. 1.

The formwork carrier 1 of FIG. 1 is provided with a foam core 2 made from PP, which is provided on both sides with a reinforcement layer of aluminum sheet 3,3′. The surface 5 of the symmetrically configured formwork carrier is formed by a layer of PP foil 4,4′ that is connected with the aluminum boards. The surface 5 has damages 48 that even reach into the core 2.

FIG. 2 shows the formwork board after the top side has been milled off by means of a blade milling machine. Only a remaining coating 41 has remained of the foil 4. The remaining coating has a wavy surface, which stems from the processing with the blade milling machine.

FIG. 3 schematically shows the welding of a new cover foil 42 onto the remaining coating 41. In the continuous process (relative movement of the carrier towards the left), the new cover foil 42 is fed to the formwork board, redirected around the roller 10, and pressed against the remaining coating 41 by the roller 10. Here, it can be recognized that the top side of the remaining coating 41, which still is to be welded, and the cover foil guided around the roller 10, on its underside, face the heat lamp 20. The heat lamp acts on the common joining zone and can therefore heat and melt both layers 41, 42 simultaneously. The diverting and pinch roller 10 at the same time provides for the exposition of the underside of the cover foil and the pressing of the respective melted-on layers (shaded area). A welding zone 43 is the result.

FIG. 4 shows the completely reprocessed formwork board with the new cover foil 42 which is provided with a smooth surface 5. The damage 48 now does not have any effects anymore on the surface quality. Edges of the cover foil that possibly protrude over the remaining coating can be removed if necessary. Now, the coating 4 practically consists of a single continuous coating of PP, but with a welding zone 43 still being detectable. Insofar, the repaired coating is not entirely homogeneous compared with a coating that has not been touched up according to the invention. 

1. Method for repairing the surface (5) of a board-shaped carrier (1) coated on at least one side with a coating (4) that is meltable under the influence of heat, wherein the underside of the coating is connected with the carrier and the top side of the coating forms the surface, comprising the following steps: a) removing the top side of the coating so that a remaining coating (41) remains on the carrier; b) applying and joining a new cover foil (42) onto the remaining coating (41) by welding.
 2. Method according to claim 1, wherein the removal of the top side of the coating is carried out by milling, in particular blade milling.
 3. Method according to claim 1, wherein a milling machine having a plurality of blades is used in blade milling.
 4. Method according to claim 1, wherein the blades of the blade milling machine are distributed and arranged in axial direction such that they are arranged in an offset manner in the direction of rotation, so that adjacent blades are biting at different times, wherein, in particular, an overlap in axial direction of adjacent blades is provided.
 5. Method according to claim 1, wherein the feed (relative) between mill and carrier is set such that the waviness of the surface of the remaining coating is smaller that between 0.02 mm or between 0.005 mm and 0.02 mm.
 6. Method according to claim 1, wherein the milling machine is arranged, in relation to the feed, such that the milling machine does not bite at the same time over the entire width of the carrier.
 7. Method according to claim 1, wherein the top side of the coating is removed in one process step.
 8. Method according to claim 1, wherein only the underside of the cover foil (42) is melted on during welding.
 9. Method according to claim 1, wherein no additional material is inserted between the remaining coating (41) and the cover foil (42) during welding.
 10. Method according to claim 1, wherein the cover foil is continuously welded to the carrier.
 11. Method according to claim 1, wherein the cover foil is guided around a roller (10) in the area of the welding zone (11), the underside of the cover foil (42) being heated in particular by means of heat lamps (20).
 12. Method according to claim 1, wherein the heat lamp acts on the underside of the cover foil (42) and the exposed top side of the remaining coating (41).
 13. Method according to claim 1, wherein the cover foil (42) is pressed by the roller (10) against the remaining coating during welding.
 14. Method according to claim 1, wherein further pinch rollers are provided.
 15. Method according to claim 1, wherein measures are carried out for straightening the repaired carrier, in particular straightening after the welding, pre-bending in the opposite direction to the internal stresses to be expected after milling and before welding, or simultaneous introduction of heat on both sides of the carrier during welding.
 16. Method according to claim 1, comprising the following steps: c) removal of the board-shaped carrier (1) from the frame of a formwork element prior to step a); d) inserting a board-shaped carrier (1) into the frame of the formwork element or another one after step b).
 17. Method according to claim 1, comprising the following steps: e) use of a carrier and damage of the surface of the carrier after step b) or d);
 18. Method according to claim 1, wherein the method is repeated several times and/or is performed on both sides of the carrier.
 19. Board-shaped carrier (1), in particular a carrier repaired according to claim 1, which is coated at least on the top side with a coating (4) meltable under the influence of heat which forms the surface of the carrier, comprising a bottom remaining coating (41), an intermediate welding zone (43), and a cover layer (42) forming the surface of the carrier.
 20. Carrier according to claim 1, characterized in that the bottom remaining coating (41), the intermediate welding zone (43) and the cover layer (42) consist of the same material, in particular of PP
 21. Carrier according to claim 1, characterized in that the coating (4, 4′) meltable under the influence of heat is provided on both sides of the carrier, wherein the coating (4′) on the underside of the carrier is perfectly homogeneous.
 22. Carrier according to claim 1, characterized in that the carrier has a core (2) of plastic, foam material, PP, loosely pressed PP particles and/or extruded PP-foam.
 23. Carrier according to claim 1, characterized in that the carrier has a reinforcement layer (3), in particular of metal, preferably aluminum.
 24. Carrier according to claim 1, characterized in that the reinforcement lacer (3) lies between the core (2) and the coating (4).
 25. Carrier according to claim 1, characterized in that the reinforcement layer (3,3′) lies on both sides of the core (2)
 26. Carrier according to claim 1, characterized in that the carrier has a symmetrical configuration, wherein the coating (4′) on the underside of the carrier can also be perfectly homogeneous.
 27. Carrier according to claim 1, characterized in that the core has a thickness of 8-20 mm; that the reinforcement layer of aluminum has a thickness of 0.3-0.6 mm, preferably of 0.35-0.45 mm; that the coating has a thickness of 0.8-1.5 mm, preferably of 1.2-1.4 mm; and/or that the thickness of the remaining coating amounts to 10%-50%, preferably 20-40% of the thickness of the coating.
 28. Carrier according to claim 1, characterized in that the carrier is so capable of bearing that it can keep unhardened concrete in shape and the coating is such that it is capable of forming an exposed-concrete surface and is easily detachable from the hardened concrete.
 29. Formwork element comprising a carrier used therein according to claim
 1. 